Following are the historical territorial acquisitions of the United States: Accession Date Area (sq.mi.) Area (km2.) Cost in dollars Original territory of the Thirteen States (western lands, roughly between the Mississippi River and Appalachian Mountains, were claimed but not administered by the states and were all ceded to the federal government or new states by 1802) 1783 892,135 2,310,619 — Annexation of the Vermont Republic 1791 9,616 24,905 — Louisiana Purchase, from France 1803 827,987 2,144,476 $15,000,000 Texas annexation 1845 389,166 1,007,935 — Oregon Territory, by treaty with Great Britain 1846 286,541 742,137 — Mexican Cession, from Mexico 1848 529,189 1,370,593 $15,000,000 Gadsden Purchase, from Mexico 1854 29,670 76,845 $10,000,000 Baker Island, unincorporated territory claimed under Guano Act of 1856 1857 0.5 1.29 — Howland Island, unincorporated territory claimed under Guano Act of 1856 1857 0.6 1.55 — Jarvis Island, unincorporated territory claimed under Guano Act of 1856 1857 1.7 4.4 — Johnston Atoll, unincorporated territory claimed under Guano Act of 1856 1857 1.1 2.85 — Alaska Purchase, from Russia 1867 591,000 1,723,336 $7,200,000 Midway Islands, annexation of unoccupied area 1867 2 5.18 — Annexation of the Republic of Hawaii 1898 6,450 16,705 — Philippines, purchased from Spain (Full independence was granted in July, 1946) 1898 115,800 299,921 $20,000,000 Puerto Rico, by treaty with Spain 1898 3,508 9,085 — Guam, by treaty with Spain 1898 209 541 — Eastern Samoa, by treaty with Great Britain and Germany 1899 76 197 — Panama Canal Zone, by treaty with Panama 1903 553 1,432 $10,000,000 (plus $250,000 annually) Guantánamo, by treaty with Cuba 1903 45 116.5 $3,386.25 (rent annually) Annexation of the Indian Territory 1906 31,069 80,468 — Danish Virgin Islands (excluding Water Island), by purchase from Denmark 1917 136 352 $25,000,000 Kingman Reef, annexed 1922 0.4 |— Swains Island, annexed 1925 0.94 2.43 — Kanton Island and Enderbury Island, joint occupation with Britain (Independent as Republic of Kiribati in 1979) 1938 6.5 16.8 — Water Island, by purchase from the East Asiatic Company, a private shipping company based in Denmark (which at the time was under German occupation) 1944 0.8 2.0 $10,000 Mariana Islands, United Nations Trust Territory; self-governing as Northern Mariana Islands 1947 179 467 — Caroline Islands, United Nations Trust Territory; 1986 most islands adopt commonwealth status as Federated States of Micronesia 1947 500 1,295 — Marshall Islands, United Nations Trust Territory; 1979 self-governing; 1986 independent as Republic of the Marshall Islands 1947 70 181 — For information on internal territorial acquisitions, see List of U.S.–Native American treaties.

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